2 Samuel 5:4

David [was] thirty years old when he began to reign; he reigned forty years.

1 Chronicles 26:31

For the Hebronites: Jeriah the chief of the Hebronites for the genealogy for the {families}. (In the fortieth year of the reign of David they were examined, and there was found among them mighty warriors of strength at Jazer in Gilead.)

1 Chronicles 29:27

And the days that he reigned over Israel [were] forty years. In Hebron he reigned seven years, and in Jerusalem he reigned thirty-three years.

Luke 3:23

And Jesus, [when he] began [his ministry], was himself about thirty years [old], being the son (as it was believed) of Joseph the [son] of Eli,

1 Kings 2:11

The days that David reigned over Israel [were] forty years; he reigned seven years in Hebron and thirty-three years in Jerusalem.

1 Chronicles 3:4

Six were born to him in Hebron. And he reigned there seven years and six months. And he reigned thirty-three years in Jerusalem.

Treasury of Scripture Knowledge

Summary

David was thirty years old when he began to reign, and he reigned forty years.

Thirty

Bible References

Thirty

Luke 3:23
And Jesus, [when he] began [his ministry], was himself about thirty years [old], being the son (as it was believed) of Joseph the [son] of Eli,

Forty

1 Chronicles 26:31
For the Hebronites: Jeriah the chief of the Hebronites for the genealogy for the {families}. (In the fortieth year of the reign of David they were examined, and there was found among them mighty warriors of strength at Jazer in Gilead.)
1 Chronicles 29:27
And the days that he reigned over Israel [were] forty years. In Hebron he reigned seven years, and in Jerusalem he reigned thirty-three years.